An exotic form of precipitation called “diamond rain”, long thought to occur deep within the icy giant planets, may be more common than previously thought.
The team of researchers experimented with material similar to that found in ice giants such as the solar system planets Neptune and Uranus, finding that the presence of oxygen increases the likelihood of diamond formation and that diamonds can form at low temperatures and pressures.
This means that diamonds can grow in a wide variety of conditions on these cold worlds. As a result, this will increase the likelihood of diamond rains pouring through the interiors of the ice giants.
On the subject: Yes, Uranus and Neptune really have a “diamond rain”
The same experiments also discovered the formation of an exotic form of water that could help explain the magnetic fields of Uranus and Neptune that have baffled astronomers so far.
The study could change our understanding of ice giants, which some scientists believe are one of the most common forms of exoplanets — planets outside the solar system.
The team of scientists, including researchers from the US Department of Energy’s SLAC National Accelerator Laboratory, as well as the Helmholtz Center Dresden-Rossendorf (HZDR) and the University of Rostock, built on previous studies of the conditions and materials inside the ice giants that observed diamond showers as they formed.
A new study predicts diamonds on Neptune and Uranus could grow to large sizes, potentially weighing up to millions of carats.
Ice giants do not have a solid surface, but become denser towards the core, meaning that over thousands of years, diamonds can sink through layers of ice. They will begin to accumulate around the solid core of the planets, forming a thick diamond layer.
(Image credit: NASA, ESA, A. Simon (Goddard Space Flight Center) and M. H. Wong (UC Berkeley) and the OPAL team) (will open in a new tab)
In addition, the team found that a new phase of water, called superionic water and sometimes referred to as “hot black ice”, formed next to the diamonds.
Superionic water exists at high temperatures and pressures, at which water molecules break down into oxygen components, forming a crystal lattice in which hydrogen nuclei float freely.
Hydrogen nuclei are positively charged, meaning that superionic water can conduct electrical current, which can create magnetic fields. This could explain the unusual magnetic fields around Uranus and Neptune.
“Our experiment demonstrates how these elements can change the conditions under which diamonds form on ice giants,” SLAC scientist and team member Silvia Pandolfi said in a statement. (will open in a new tab) “If we want to model planets accurately, we need to get as close as possible to the actual composition of the planet’s interior.”
A more complex picture of diamond formation
Siegfried Glenzer, director of High Energy Density at SLAC, explained that the situation inside planets such as ice giants is complex because many chemicals are involved in the formation of diamonds.
“The previous work was the first time we directly observed the formation of diamonds from any mixture,” said Glenzer. “Since then, quite a few experiments have been carried out with various pure materials. Here we wanted to find out what kind of effect these additional chemicals have.”
Although the team began their experiments using a plastic material made up of a mixture of hydrogen and carbon, elements commonly found in ice giants, this has been replaced with PET plastic in the latest iteration.
Familiar to us on Earth due to its use in packaging, bottles and containers, PET can be used to more closely mimic the conditions inside ice giants.
“PET has a good balance between carbon, hydrogen and oxygen to mimic the activity of icy planets,” said HZDR physicist and University of Rostock professor Dominik Kraus.
By creating shock waves in PET using a high-power optical laser—part of the Matter in Extreme Conditions (MEC) instrument at SLAC—the team was able to investigate what was happening in the plastic using X-ray pulses from a Linac Coherent Light Source. LCLS).
This allowed them to observe how the atoms inside the PET arranged themselves into diamond-shaped regions, measuring the rate at which these regions grew.
In addition to finding diamond-shaped regions that grow to be about a few nanometers wide, the scientists also found that the presence of oxygen in PET means that nanodiamonds grow at lower pressures and lower temperatures than previously observed.
“The effect of oxygen was to accelerate the splitting of carbon and hydrogen and thus stimulate the formation of nanodiamonds,” Kraus said. “This meant that carbon atoms could combine more easily and form diamonds.”
Nanodiamonds: good things come in small packages
The research could potentially point the way to a new method of making diamonds smaller than 1 micrometer, known as “nanodiamonds,” which can be produced when cheap PET plastic is shock-compressed with a laser.
“The way to produce nanodiamonds currently is to take a bunch of carbon or diamond and blow it up with explosives,” said SLAC scientist and team member Benjamin Ofori-Okai. In this experiment, we observe different reactivity of the same species at high temperature and pressure.”
Ofori-Okai added that laser manufacturing could offer a cleaner and more easily controlled method for producing nanodiamonds. “If we can come up with ways to change some aspects of the reactivity, we can change how fast they form and therefore how big they get,” he continued.
Nanodiamonds have many potential applications in medicine, including drug delivery, non-invasive surgery, and medical sensors, as well as in the growing field of quantum technology. This means the scientists’ findings could have serious implications that could be closer to home than the ice giants lurking on the outskirts of the solar system.
The scientists involved in this study will now attempt to conduct experiments using liquid samples containing chemicals such as ethanol, water and ammonia, some of the main components of the ice giants, to get a better picture of what happens under the icy atmosphere of these cold worlds. .
“The fact that we can recreate these extreme conditions to see how these processes take place on a very fast and very small scale is impressive,” said SLAC scientist and collaborator Nicholas Hartley. “The addition of oxygen brings us closer than ever to seeing the full picture of these planetary processes, but there is still a lot of work to be done.
“This is a step towards getting the most realistic mixture possible and understanding how these materials actually behave on other planets.”
The team’s research is published in the latest issue of Science Advances. (will open in a new tab).
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